1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to an image display apparatus and a method of providing a high quality image, and more particularly, to an image display apparatus which analyzes characteristics of an input image signal and dynamically processes the signal based on the analysis to provide a high quality image display.
2. Description of the Related Art
Use of an image display apparatus, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display panel (PDP), and a digital light processing (DLP), has been increasing. Accordingly, a greater enhanced image quality of the image display apparatus is necessary. In order to meet such demands, various suggestions to enhance image quality have been made.
Each type of image display apparatus has its own display characteristics to output an optimum image. For example, PDP displays images digitally, so they have different gradation values depending on the size of the digital data. The method of displaying through the PDP will be briefly explained below with reference to FIGS. 1 and 2.
FIG. 1 illustrates a display method of a related art image display apparatus.
FIG. 1 shows an example where a unit frame constituting a screen is time-divided into eight sub-fields SF1, SF2, . . . , SF8. Each of the sub-fields SF1, SF2, . . . , SF8 is divided into reset regions (not shown), address regions A1, A2, . . . , A8, and sustain regions S1, S2, . . . , S8.
Cells are set to an initial state in the reset regions, and turning cells on or off is determined based on the display data in the address regions A1, A2, . . . , A8. Also, for cells to turn on, the display discharge is shown in the sustain regions S1, S2, . . . , S8 so that image is displayed through the screen.
The illuminating periods 1T, 2T, . . . , 128T of the sustain regions S1, S2, . . . , S8 are formed at a proportion of 1:2:4:8:16:32:64:128. By selecting an appropriate sub-field to display from the eight sub-fields SF1, SF2, . . . , SF8, any sub-field can realize 256 gradations, including the zero gradation, which does not have display discharge.
Sustain pulses are supplied to the scan electrode and the sustain electrode of the panel in turn in the sustain regions S1, S2, . . . , S8, in order to generate a display discharge. The contrast varies depending on the number of sustain pulses supplied in the same sustain region S1, S2, . . . , S8. Therefore, the number of sustain pulses can be adjusted based on the average picture level (APL) of the input image signal (FIG. 2).
FIG. 2 is a graphical representation of the number of sustain pulses as a function of the APL in a related art image display apparatus. FIGS. 3A and 3B show images having the same APL displayed through the related art image display apparatus.
Referring to FIG. 2, the number of sustain pulses is increased to improve contrast when the screen is relatively dark due to a low APL. On the contrary, the number of sustain pulses is decreased to reduce power consumption when the APL is high and the screen is relatively bright. Automatic power control (APC) can be achieved by maintaining the power consumption at a constant level, regardless of the contrast of the screen.
However, when the APL of the input image signals is same, the same number of sustain pulses is supplied. FIGS. 3A and 3B show an example of inputting different types of image signals having the same APL, in which the same number of sustain pulses is supplied. The image display apparatus displaying the resultant pattern as shown in FIG. 3B needs relatively large power consumption, and the driving board is under stress. Additionally, the image with high contrast is saturated on the screen, and the image quality degrades.